<?php 
$username=$_GET['username'];
$db = new DBManager ( 'localhost', 'root', '', 'iumus' );
$query='SELECT * from utente where username='.'\''.$username.'\';';
echo $query;
$result=$db->executeQuery ($query);
$row=mysql_fetch_array($result);
if(isset($row))
return false;
else return true;
?>